Adhesion to plastic with block copolymers obtained using raft

ABSTRACT

An aqueous coating composition (which optionally can coat plastic substrates) the composition comprising a block copolymer and a polymer P; where the block copolymer comprises at least blocks [A] x [B] y ; where at least block [A] is obtained by a controlled radical polymerisation of at least one ethylenically unsaturated monomer via a reversible addition-fragmentation chain transfer (RAFT) mechanism (optionally in solution in the presence of a control agent and a source of free radicals); and wherein block [A] comprises 20 to 100 mol % of ethylenically unsaturated monomer units bearing water-dispersing functional groups; wherein block [B] comprises 20 to 100 mol % of ethylenically unsaturated monomer units bearing plastic adhesion promoting functional groups; and wherein polymer P is prepared in the presence of blocks [A] x [B] y . The compositions may be used to coat plastic substrates, foam; surfaces having low surface energy, hydrophobic substrates and/or polyolefins.

This application is a continuation of U.S. application Ser. No.12/935,991 filed on 20 Dec. 2010, which is the U.S. national phase ofInternational Application No. PCT/EP2009/053891, filed 1 Apr. 2009,which designated the U.S. and claims priority to European ApplicationNo. 08103288.0, filed 1 Apr. 2008, the entire contents of each of whichare hereby incorporated by reference.

This invention relates to a process for obtaining an aqueous coatingcomposition comprising a block copolymer and polymer where thecomposition is preferably suitable for application to a plasticsubstrate more preferably a hydrophobic plastic substrate. It is wellrecognised that adhesion to plastic substrates and in particularhydrophobic plastic substrates is generally hard to achieve. Foradhesion to polyolefins, especially to polyolefins such aspolypropylene, a hydrophobic polymer would be desirable. A problem withthe sole use of such hydrophobic polymers is that they tend to lackother properties, like good mechanical properties such as flexibilityand furthermore they may be difficult to pigment. Pigment wetting oftenrequires the presence of hydrophilic groups which will be lessfavourable for wetting of hydrophobic substrates.

Coatings for plastic substrates need to take into account the lowsurface energy of plastic parts and the chemical similarity between thecoating materials and the plastic substrate. Coatings for plasticsubstrates must adhere well to the plastic part for the life of thecomponent and the following criteria are often used to measure theperformance: adhesion, chemical resistance, impact performance andscratch resistance.

The adhesion of the coating to the plastic substrate is mainlydetermined by surface tension characteristics of the coating and thesubstrate and interdiffusion of the coating into the substrate.

Surface tension will directly influence a coating's ability to wet out,to penetrate, and to adhere to the porous structure of a surface. It isgenerally seen that the lower the surface tension, the more problematicit is to get good adhesion of the coating on the substrate.

The surface tension of the coating should be lower than the surfacetension of the substrate to enable wetting of the coating on the surfaceof the substrate. Efficient wetting will maximize the adhesion. Surfaceroughness may also be an important parameter in certain cases as“mechanical interlocking” is another way to improve adhesion.

Interdiffusion is the main adhesion mechanism for amorphous plastics,especially in the case of solvent based coating systems. The solvent isused to diffuse the polymer in the coating into the plastic substrate toprovide for molecular interlocking. Ideally, this solvent should beselected from those that are good solvents for the polymers of thecoating composition, and for the polymer constituting that of theplastic substrate.

From an environmental point of view there is however an increasing needto reduce the amount of organic solvents in such coating compositions.In this respect waterborne binders are clearly preferred overconventional solventborne binders. The use of waterborne binders incoating compositions for application to hydrophobic plastic substratesmay however give issues regarding wetting and or polymer interdiffusion.

A common method to enhance the coating adhesion to hydrophobic plasticswith a relatively low surface tension like polyolefins and fluorocarbonsis to employ surface pretreating processes. Surface treatments includechemical and physical methods such as chemical etching and coronadischarge, and typically result in the formation of polar groups on thesurface such as pendant hydroxyl, chloro, amino and carboxyl groups. Theintroduction of polar groups on the plastic substrate surface canprovide improved wetting (as the surface tension is increased) andpotential chemical interaction with the applied coating composition,which can result in improved adhesion. Such surface pretreating methodshowever are often costly and time-consuming, and tend to negativelyaffect the plastic surface physical properties.

Clearly a need exists for water-based binders that provide the desiredcombination of good adhesion to (hydrophobic) plastic substrates andgood mechanical properties and chemical or stain resistances.

There is an increased scope of polymerisation methods available foradaptation to polymerisations to make waterborne polymers. In the designof such waterborne polymers for plastic coating applications it would bevery advantageous to be able to control the polymer binder compositionin terms of polymer chain composition and chain architecture. Forexample, for obtaining good adhesion to hydrophobic plastics it isdesirable to use hydrophobic polymers that are preferably of the samechemical composition as the plastic polymer chains to maximise thedegree of polymer chain interdiffusion. For waterborne polymers howeverthe degree of chain interdiffusion is limited by the significant amountof hydrophilic comonomers that typically need to be incorporatedrandomly in the hydrophobic polymer backbone to make the polymerwater-dispersable. In addition, crosslinking of the binder compositioncan provide improved coating performance in terms of for examplechemical resistances, but will often have a negative effect on adhesion.It would therefore be desirable to separate out water-dispersing and orcrosslinking functionality from adhesive functionality within thepolymer binder.

In particular controlled radical polymerisation techniques such asnitroxide mediated polymerisation (NMP), atom transfer radicalpolymerisation (ATRP), and degenerative transfer techniques such asreversible addition-fragmentation chain transfer (RAFT) polymerisationhave been investigated as means to control polymer chain composition andarchitecture.

EP020125, EP381029, EP381030, EP468644, EP517379 and EP560508 disclosemonomers suitable for use in polymers to give improved adhesion of thepolymers to plastic substrates. However, none of prior art examplesdiscloses the advantageous use of an adhesion promoting block copolymerthat provides the desired adhesion of the coating composition to plasticsubstrates.

US2004/0071871 (and US2004/0082494) discloses the use of an amphiphilicblock copolymer prepared using RAFT polymerization as an additive forfilm forming compositions to promote adhesion on a low energy surfacesuch as a plastic or thermoplastic polymer surface. The amphiphilicblock copolymer provides improved wetting of the film forming bindercomposition, but does not provide (significant) improved adhesion of thebinder composition to (hydrophobic) plastic substrates.

US2002/0198347 describes a surface active block copolymer comprising atleast one hydrophilic block and at least one hydrophobic block, preparedby living radical polymerisation. The M_(n) of the block copolymer isbetween 1,000 and 50,000 D, the Tg of the hydrophobic block between −100and +30° C. and having a specific surface tension. US2002/0198347 doesnot teach the advantageous use of a block copolymer—binder compositionfor obtaining the desired combination of good adhesion to hydrophobicplastic substrates and good mechanical properties and good chemical orstain resistances. Furthermore, the block copolymers as disclosed in theprior art may provide adhesion to plastic substrates through improvedwetting of the coatings, however, the overall level of adhesion islimited as the block copolymers do not provide improved interdiffusionbetween the plastic substrate and the coating composition.

WO 02/090392 discloses an acrylic acid (AA)/butyl acrylate (BA) blockcopolymer. Although the copolymer contains the hydrophobic monomer BA itis not present in an amount which could be considered to aid adhesion toplastic.

EP560508 discloses a coating composition for polyolefins includingpolypropylene comprising an aqueous emulsion of a polymer systemcomprising a polymer which imparts polyolefin adherability.

WO08/00622 relates to a method for coating substrates of polyolefins bytreatment with an aqueous dispersion containing a copolymer, a copolymerof a C₃₋₁₀ olefin and at least one amphiphilic block copolymer.

We have now surprisingly found that according to the present inventionthe reversible addition-fragmentation chain transfer (RAFT)polymerisation process provides a useful route for preparing awaterborne polymer composition that provides improved adhesion toplastic substrates and in particular hydrophobic plastic substrates incombination with good general coating properties, such as goodmechanical properties, pigment wetting and chemical resistances. Thisadvantageous combination of properties may be achieved with blockcopolymers comprising one block having a specific concentration ofplastic adhesion promoting monomers and one block having a hydrophiliccharacter. Furthermore the reversible addition-fragmentation chaintransfer (RAFT) polymerisation process may be used to provide a usefulroute for making water-based (or water-dispersable) block copolymersthat contain a plastic adhesion promoting block next to at least ahydrophilic block.

When a suitable polymer is prepared in the presence of such a blockcopolymer it means that waterborne coatings with an advantageouscombination of coating properties can be obtained that is difficult toachieve otherwise.

RAFT polymerisation in for example a solution can avoid the undesirablehomopolymerisation of monomers with a high water solubility and providesthe possibility to fully control the polymer chain composition and thechain architecture of water-based polymers. By making an [A][B] type ofblock copolymer, followed by preparing a polymer P, the above problemsmay be mediated, and waterborne polymer compositions can be obtainedthat have the desired combination of properties such as good filmformation, good mechanical properties, chemical coating propertiesand/or good adhesion to plastic substrates (for example hydrophobicplastic substrate).

An aspect of the present invention relates to aqueous compositions thatare capable of being applied to a plastic substrate to form a coatingthereon and a process for obtaining such compositions (which are alsoreferred to herein as aqueous plastic coating compositions).

It is an object of the present invention to address some or all of theproblems described herein.

According to the invention there is provided a process for preparing aaqueous coating composition comprising a block copolymer and a polymerP; wherein the block copolymer comprises at least blocks [A]_(x)[B]_(y),where at least block [A] is obtained by a controlled radicalpolymerisation of at least one ethylenically unsaturated monomer via areversible addition-fragmentation chain transfer (RAFT) mechanism; whereblock [A] comprises:

-   -   i) 0 to 50 mol % of ethylenically unsaturated monomer units        bearing crosslinking functional groups;    -   ii) 20 to 100 mol % of ethylenically unsaturated monomer units        bearing water-dispersing functional groups;    -   iii) 0 to 50 mol % of ethylenically unsaturated monomers units        selected from linear or branched C₁ to C₈ alkyl(meth)acrylate        monomers;    -   iv) 0 to 5 mol % of ethylenically unsaturated monomer units        bearing plastic adhesion promoting functional groups; and    -   v) 0 to 10 mol % of ethylenically unsaturated monomers units        different from those from i), ii), iii)+iv);    -   where i), ii), iii), iv)+v) add up to 100%;    -   block [A] has an average degree of polymerisation x, where x is        an integer from 3 to 80;    -   where block [B] comprises:    -   i) 0 to 5 mol % of ethylenically unsaturated monomer units        bearing crosslinking functional groups;    -   ii) 0 to 15 mol % of ethylenically unsaturated monomer units        bearing water-dispersing functional groups;    -   iii) 0 to 50 mol % of ethylenically unsaturated monomers units        selected from linear or branched C₁ to C₈ alkyl(meth)acrylate        monomers;    -   iv) 20 to 100 mol % of ethylenically unsaturated monomer units        bearing plastic adhesion promoting functional groups; and    -   v) 0 to 10 mol % of ethylenically unsaturated monomers units        different from those from i), ii), iii)+iv);    -   where i), ii), iii), iv)+v) add up to 100%;    -   block [B] has an average degree of polymerisation y, where y is        an integer ≧10, where y>x; and    -   where polymer P is obtained in the presence of the block        copolymer by an emulsion polymerisation process, and comprises:    -   i) 0 to 20 wt % of ethylenically unsaturated monomer units        bearing crosslinking functional groups;    -   ii) 0 to 15 wt % of ethylenically unsaturated monomer units        bearing water-dispersing functional groups;    -   iii) 50 to 100 wt % of ethylenically unsaturated monomers units        selected from linear or branched C₁ to C₈ alkyl(meth)acrylate        monomers;    -   iv) 0 to 50 wt % of ethylenically unsaturated monomer units        bearing plastic adhesion promoting functional groups; and    -   v) 0 to 10 mol % of ethylenically unsaturated monomers units        different from those from i), ii), iii)+iv);    -   where i), ii), iii), iv)+v) add up to 100%.

Preferably block [A] is obtained and/or obtainable by a controlledradical polymerisation of at least one ethylenically unsaturated monomervia a reversible addition-fragmentation chain transfer mechanism insolution in the presence of a control agent and a source of freeradicals.

It is preferred that the compositions of the invention are coatingcompositions capable of being applied to plastic substrates to from acoating thereon.

The average degree of polymerisation x (or y) is determined by the totalmolar amount of monomers in block [A] (or [B]) divided by the totalmolar amount of control (RAFT) agent.

Preferably integer x is in the range of from 4 to 70 and more preferably5 to 60.

Preferably integer y is the range of from 10 to 500, more preferably 20to 300 and most preferably 25 to 200.

Preferably the block copolymer obtained by the process of the inventioncomprises in the range of from 2 to 50 wt %, more preferably 4 to 40 wt% and especially 5 to 35 wt % of block [A] based on the weight of blocks[A] and [B].

Preferably the composition obtained by the process of the inventioncomprises in the range of from 0.5 to 65 wt %, more preferably 2 to 50wt % and most preferably 3 to 40 wt % of blocks [A][B] together, basedon the weight of blocks [A][B] and polymer P.

The term “comprising” as used herein means that the list thatimmediately follows is non exhaustive and may or may not include anyother additional suitable items, for example one or more furtherfeature(s), component(s), ingredient(s) and/or substituent(s) asappropriate. “Substantially comprising” as used herein means a componentor list of component(s) is present in a given material in an amountgreater than or equal to about 90%, preferably ≧95%, more preferably≧98% by weight of the total amount of the given material. The term“consisting of” as used herein mean that the list that follows isexhaustive and does not include additional items.

For all upper and lower boundaries of any parameters given herein, theboundary value is included in each range for each parameter. Allcombinations of minimum and maximum values of the parameters describedherein may be used to define the parameter ranges for variousembodiments and preferences of the invention.

It will be understood that the total sum of any quantities expressedherein as percentages cannot (allowing for rounding errors) exceed 100%.For example the sum of all components of which the composition of theinvention (or part(s) thereof) comprises may, when expressed as a weight(or other) percentage of the composition (or the same part(s) thereof),total 100% allowing for rounding errors. However where a list ofcomponents is non-exhaustive the sum of the percentage for each of suchcomponents may be less than 100% to allow a certain percentage foradditional amount(s) of any additional component(s) that may not beexplicitly described herein.

Unless the context clearly indicates otherwise, as used herein pluralforms of the terms herein (for example monomer, polymer, control agent,initiator and/or block) are to be construed as including the singularform and vice versa.

As used herein chemical terms (other than IUPAC names for specificallyidentified compounds) which comprise features which are given inparentheses—such as (alkyl)acrylate, (meth)acrylate and/or(co)polymer—denote that that part in parentheses is optional as thecontext dictates, so for example the term (meth)acrylate denotes bothmethacrylate and acrylate.

The substituents on the repeating unit of the polymer and/or blockcopolymer may be selected to improve the compatibility of the materialswith the polymers and/or resins in which they may be formulated and/orincorporated for the uses described herein. Thus the size and length ofthe substituents may be selected to optimise the physical entanglementor interlocation with the resin or they may or may not comprise otherreactive entities capable of chemically reacting and/or crosslinkingwith such other resins as appropriate.

A block copolymer is understood to be a copolymer comprising at leasttwo successive sections of blocks of monomer units of different chemicalconstitutions. The block copolymers of the invention can therefore bediblock, triblock or multiblock copolymers. Block copolymers may belinear, branched, star or comb like, and have structures such as [A][B],[A][B][A], [A][B][C], [A][B][A][B], [A][B][C][B] etc. Preferably theblock copolymer is a linear diblock copolymer of structure [A][B], or alinear triblock copolymer of structure [A][B][A]. Block copolymers mayhave multiple blocks [A], [B] and optionally [C] in which case the blockcopolymer is represented as for example [A]_(x)[B]_(y) or[A]_(x)[B]_(y)[C]_(z), where x, y and z are the degrees ofpolymerisation (DP) of the corresponding blocks [A], [B] or [C].

Furthermore any of the blocks in the block copolymer could be either ahomopolymer, meaning only one type of monomer, or a copolymer, meaningmore than one type of monomer. In case of a copolymer type of block thecomposition could be either random or gradient like, depending on theprocessing conditions used. A block with a gradient composition isunderstood to be a block having a continuously changing monomercomposition along the block.

The block copolymer may be oligomeric comprising only a few repeat units(such as up to 10) where typically any change in the number of repeatunits may significantly effect the overall properties of the oligomer.Alternatively the block copolymer may be a polymer with many more repeatunits in which typically a small change in the number of repeat units inthe polymer has little or no effect on the polymer's properties.

The term “controlled radical polymerisation” is to be understood as aspecific radical polymerisation process, also denoted by the term of“living radical polymerisation”, in which use is made of control agents,such that the block copolymer chains being formed are functionalised byend groups capable of being reactivated in the form of free radicals byvirtue of reversible transfer or reversible termination reactions.

Controlled radical polymerisation processes in which reversibledeactivation of radicals proceeds by reversible transfer reactionsinclude for example the process for radical polymerisation controlled bycontrol agents, such as reversible transfer agents of the dithioester(R—S—C(═S)—R′) type as described in WO98/01478 and WO99/35178, theprocess for radical polymerisation controlled by reversible transferagents of trithiocarbonate (R—S—C(═S)—S—R′) type as described in forexample WO98/58974, the process for radical polymerisation controlled byreversible transfer agents of xanthate (R—S—C(═S)—OR′) type as describedin WO98/58974, WO00/75207 and WO01/42312, and the process for radicalpolymerisation controlled by reversible transfer agents ofdithiocarbamate (R—S—C(═S)—NR₁R₂) type as described for example inWO99/31144 and WO99/35177.

Such controlled radical polymerisations are known in the art asreversible addition-fragmentation chain transfer (RAFT) polymerisation(WO98/01478; Macromolecules 1998 31, 5559-5562) or macromolecular designvia interchange of xanthates (MADIX) polymerisation (WO98/58974;Macromolecular Symposia 2000 150, 23-32).

“Addition-fragmentation” is a two-step chain transfer mechanism whereina radical addition is followed by fragmentation to generate a newradical species.

When preparing for example a block copolymer in the presence of thecontrol agent, the end of the growing block is provided with a specificfunctionality that controls the growth of the block by means ofreversible free radical deactivation. The functionality at the end ofthe block is of such a nature that it can reactivate the growth of theblock in a second and/or third stage of the polymerisation process withother ethylenically unsaturated monomers providing a covalent bondbetween for example a first and second block [A] and [B] and with anyfurther optional blocks.

Optionally the chain end functionality of block copolymer [A]_(x)[B]_(y)is retained to assist with the covalent bond formation between blockcopolymer [A]_(x)[B]_(y) and any further optional blocks and or polymerP.

Preferably the block copolymer is obtained from a controlled radicalpolymerisation process employing as a control agent, a reversibletransfer agent. Reversible transfer agents may be one or more compoundsselected from the group consisting of dithioesters, thioethers-thiones,trithiocarbonates, dithiocarbamates, xanthates and mixtures thereof.

Reversible transfer agents also include symmetrical transfer agents. Anexample is a dibenzyltrithiocarbonate such as.C₆H₅CH₂—S—C(═S)—S—CH₂C₆H₅.

Control agents of the xanthate type have low transfer constants in thepolymerization of styrenes and in particular methacrylate type monomerswhich may result in a higher polydispersity and/or poor chain growthcontrol of the resultant polymers and may be considered as lesseffective RAFT control agents, although the actual mechanism involved issimilar to the reversible-addition fragmentation chain transfer (RAFT)mechanism described in WO98/01478. Reversible transfer agents of thedithioester type like for example benzyl dithiobenzoate derivatives aregenerally considered as having a high transfer constant and being moreeffective RAFT control agents.

Transfer constants are descibed in WO98/01478. “Chain transfer constant”(C_(tr)) means the ratio of the rate constant for chain transfer(k_(tr)) to the rate constant for propagation (k_(p)) at zero conversionof monomer and CTA. If chain transfer occurs by addition-fragmentation,the rate constant for chain transfer (k_(tr)) is defined as follows:

k _(tr) =k _(add) ×[k _(β)/(k _(−add) +k _(β))]

where k_(add) is the rate constant for addition to the CTA and k_(−add)and k_(β) are the rate constants for fragmentation in reverse andforward directions respectively.

In an embodiment of the invention the control agent preferably has atransfer constant C_(tr)=(k_(add)/k_(p))[k_(β)/(k_(−add)+k_(β))] of lessthan 50, more preferably less than 20 and most preferably below 10.

Preferably the block copolymer is obtained from a controlled radicalpolymerisation process employing a control agent having a group withformula

—S—C(═S)—.

Preferably the block copolymer is obtained from a controlled radicalpolymerisation process employing xanthates and/ordibenzyltrithiocarbonate.

Preferably the block copolymer is obtained from a controlled radicalpolymerisation process employing a xanthate such asO-ethyl-S-(1-methoxycarbonyl)ethyl dithiocarbonate [RSC(═S)—OC₂H₅ whereR═—CH(CH₃)—C(═O)—OCH₃].

For clarity, control agents for use in RAFT do not includediphenylethylene, which although it is a control agent can not be usedas a RAFT control agent, i.e. for a RAFT polymerisation mechanism.

Component I)

Conveniently component i) may comprise ethylenically unsaturated monomerunits (usually C₁₋₁₂alkyl(meth)acrylates) bearing crosslinkingfunctional groups such as reactive double bonds [for exampleallyl(meth)acrylate], epoxy [for example glycidyl(meth)acrylate],hydroxy [for example hydroxyalkyl(meth)acrylates such ashydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,4-hydroxybutyl(meth)acrylate and their modified analogues like ToneM-100 (available commerically from Union Carbide Corporation under thistrade name)], anhydride (for example maleic anhydride), amine [forexample dimethylaminoethyl(meth)acrylate], acetoacetoxy [such asacetoacetoxyethyl(meth)acrylate, for example for crosslinking withamines], keto or aldehyde [such as (meth)acrolein or diacetoneacrylamide, for example for crosslinking with additive crosslinkersincluding dihydrazides (such as adipic acid dihydrazide) or silanefunctional groups], combinations thereof on the same monomer and/ormixtures thereof. Preferred monomers suitable for crosslinking includefor example hydroxyalkyl(meth)acrylates, glycidyl(meth)acrylates anddiacetone acrylamide.

Monomers which may also provide some water-dispersing properties, suchas hydroxyalkyl(meth)acrylates like for examplehydroxyethyl(meth)acrylate (HE(M)A), are considered herein asethylenically unsaturated monomers providing crosslinking functionalgroups.

Preferably block [A] comprises 0 to 35 mol %, more preferably 0 to 25mol % and most preferably 2 to 25 mol % of component i).

Preferably block [B] comprises 0 to 3 mol %, more preferably 0 mol % ofcomponent i).

Preferably polymer P comprises 0 to 15 wt % of component i).

Component II)

Conveniently component ii) may comprise ethylenically unsaturatedmonomer units (preferably having at least 3 carbon atoms e.g. from 3 to20 carbon atoms) bearing non-ionic, ionic or potentially ionicwater-dispersing functional groups. Preferably the water-dispersingfunctional groups bearing ionic or potentially ionic functional groupsneed to be in their dissociated (i.e. salt) form to effect theirwater-dispersing action. If they are not dissociated they are consideredas potential ionic groups which become ionic upon dissociation. Theionic water-dispersing groups are preferably fully or partially in theform of a salt in the final composition of the invention. Ionic orpotentially ionic water-dispersing groups include cationicwater-dispersing groups such as basic amine groups, quaternary ammoniumgroups, and anionic water-dispersing groups such as acid groups, forexample phosphoric acid groups, sulphonic acid groups, and carboxylicacid groups.

There are also potentially ionic functional monomers that may becomecationic upon addition of acid, such as dimethylaminoethyl(meth)acrylate, dimethylamino propyl(meth)acrylate, anddimethylamino propyl(meth)acrylamide. Such potentially ionic functionalmonomers may contribute to improved adhesion and may also improvestability or appearance on specific substrates such as wood.

Preferably any ionic water-dispersing groups are anionic waterdispersing groups.

Preferred ethylenically unsaturated monomer units bearing ionic orpotentially ionic water-dispersing functional groups include(meth)acrylic acid, itaconic acid, maleic acid, β-carboxyethyl acrylate,monoalkyl maleates (for example monomethyl maleate and monoethylmaleate), citraconic acid, styrenesulphonic acid, sodiumstyrenesulphonate, vinylbenzylsulphonic acid, vinylsulphonic acid,sodium vinylsulphonate, acryloyloxyalkyl sulphonic acids (for exampleacryloyloxymethyl sulphonic acid), 2-acrylamido-2-alkylalkane sulphonicacids (for example 2-acrylamido-2-methylethanesulphonic acid),2-methacrylamido-2-alkylalkane sulphonic acids (for example2-methacrylamido-2-methylethanesulphonic acid),mono(acryloyloxyalkyl)phosphates (for example,mono(acryloyloxyethyl)phosphate and mono(3-acryloyloxypropyl)phosphates)and mono(methacryloyloxyalkyl)phosphates, and/or mixtures thereof.

Ethylenically unsaturated monomer units bearing water-dispersingfunctional groups may also include ethylenically unsaturated monomerunits bearing non-ionic water dispersing groups such as pendantpolyoxyalkylene groups, more preferably polyoxyethylene groups such asmethoxy(polyethyleneoxide(meth)acrylate), hydroxy polyethyleneglycol(meth)acrylates, alkoxy polyproplene glycol(meth)acrylates andhydroxy polypropylene glycol(meth)acrylates, preferably having a numberaverage molecular weight of from 350 to 3,000 g/mol. Examples of suchethylenically unsaturated monomers which are commercially availableinclude w-methoxypolyethylene glycol(meth)acrylate. Other vinyl monomersproviding non-ionic water dispersible groups include(meth)acrylamidemono(methacryloyl oxethyl)phosphate and acrylamide.

Preferably ethylenically unsaturated monomer units bearingwater-dispersing functional groups are selected from the groupconsisting of ionic water-dispersing or potentially ionicwater-dispersing functional groups with a pKa<4.5, non-ionicwater-dispersing groups and mixtures thereof.

Monomers which may also provide some crosslinking properties such as(meth)acrylic acid, are considered herein as monomers providingwater-dispersing functional groups.

Preferably 0 to 16 mol % of ethylenically unsaturated monomer unitsbearing non-ionic water-dispersing groups is used, more preferably 0 to10 mol % and most preferred 0 to 7 mol % based on the block copolymer.

Preferably block [A] comprises 0 to 35 mol %, more preferably 0 to 25mol % and most preferably 2 to 20 mol % of ethylenically unsaturatedmonomer units bearing non-ionic water dispersing groups.

Preferably block [B] comprises 0 to 16 mol %, more preferably 0 to 12mol % and most preferably 2 to 7 mol % of ethylenically unsaturatedmonomer units bearing non-ionic water dispersing groups.

Preferably block [A] comprises 50 to 100 mol %, more preferably 75 to100 mol % of component ii).

Preferably block [B] comprises 0 to 10 mol %, more preferably 0 to 5 mol% and especially 1 to 10 mol % of component ii).

Preferably polymer P comprises 0 to 10 wt % and more preferably 0 to 5wt % of component ii).

Component III)

Conveniently component iii) may comprise linear or branched acyclicesters of acrylic acid and methacrylic acid of formula 1

CH₂═CR⁵—COOR⁴   Formula 1

wherein R⁵ is H or methyl and R⁴ is optionally substituted C₁ to C₈alkyl, aryl or (alkyl)aryl which are also known as acrylic ormethacrylic monomers, examples of which are methyl(meth)acrylate,ethyl(meth)acrylate, propyl(meth)acrylate (all isomers),butyl(meth)acrylate (all isomers) and 2-ethylhexyl(meth)acrylate.

Preferably block [A] comprises 0 to 35 mol %, more preferably 0 to 25mol % of component iii)

Preferably block [B] comprises 0 to 35 mol %, more preferably 0 to 25mol % of component iii).

Preferably polymer P comprises 60 to 100 wt % and more preferably 70 to100 wt % of component iii).

Component IV)

Conveniently component iv) may comprise monomers selected from the groupconsisting of styrenic monomers such as styrene, a-methylstyrene,t-butyl styrene, chloromethyl styrene, C₆ to C₂₀ optionally substitutedalkyl, cyclo alkyl and or aryl(meth)acrylate monomers such asisobornyl(meth)acrylate, isodecyl(meth)acrylate, lauryl(meth)acrylate,tridecyl(meth)acrylate, tetradecyl(meth)acrylate,hexadecyl(meth)acrylate, octadecyl(meth)acrylate(=stearyl(meth)acrylate), dicyclopentenyloxymethyl(meth)acrylate,benzyl(meth)acrylate, 2-phenoxyethyl(meth)acrylate,3,3,5-trimethyl-cyclohexyl(meth)acrylate, p-methylphenyl(meth)acrylate,1-naphtyl(meth)acrylate, 3-phenyl-n-propyl(meth)acrylate and2-phenyl-aminoethyl(meth)acrylate, C₆ to C₂₀ optionally substitutedalkyl(meth)acrylamide monomers such as t-octyl(meth)acrylamide andn-decyl(meth)acrylamide, vinylic monomers such as vinyl toluene, vinylesters of versatic acid like VEOVA® 9 or VEOVA® 10, vinyl chloride andvinylidene chloride, and mixtures thereof.

Preferably the ethylenically unsaturated monomer units bearing plasticadhesion promoting functional groups are selected from the groupconsisting of C₆ to C₂₀ (preferably C₆ to C₁₅) optionally substitutedalkyl, cyclo alkyl and or aryl(meth)acrylate monomers, styrenicmonomers, C₆ to C₂₀ (preferably C₆ to C₁₅) optionally substitutedalkyl(meth)acrylamide monomers, vinylic monomers and mixtures thereof.

More preferably the ethylenically unsaturated monomer units bearingplastic adhesion promoting functional groups are selected from the groupconsisting of C₆ to C₂₀ (preferably C₆ to C₁₅) optionally substitutedalkyl, cyclo alkyl and or aryl(meth)acrylate monomers and mixturesthereof.

Preferably block [A] comprises 0 to 2 mol %, more preferably 0 mol % ofcomponent iv).

Preferably block [B] comprises 50 to 100 mol %, more preferably 75 to100 mol % of component iv).

When the plastic substrate is polyolefinic, particularly polypropyleneor a copolymer of propylene and another olefin like ethylene, thenpreferably component iv) of block [B] comprises at least 50 mol %, andmore preferably at least 70 mol % and especially at least 90 mol % ofisobornyl(meth)acrylate.

Preferably polymer P comprises 5 to 50 wt %, more preferably 4 to 40 wt% and especially 10 to 40 wt % of component iv). When the plasticsubstrate is a polyolefin, particularly polypropylene or a copolymer ofpropylene and another olefin like ethylene, then preferably componentiv) of polymer P comprises at least 50 wt %, and more preferably atleast 70 wt % and especially at least 90 wt % of isobornyl(meth)acrylate.

Component V)

Conveniently component v) may comprise dienes such as 1,3-butadiene andisoprene; vinyl monomers such as acrylonitrile, methacrylonitrile; vinylhalides such as vinyl chloride; vinylidene halides such as vinylidenechloride; vinyl esters such as vinyl acetate, vinyl propionate, vinyllaurate; heterocyclic vinyl compounds; alkyl esters of mono-olefinicallyunsaturated dicarboxylic acids such as di-n-butyl maleate and di-n-butylfumarate; amides of unsaturated carboxylic acids such as(meth)acrylamide, N-methylol(meth)acrylamide andN-alkyl(meth)acrylamides.

The Tg of a polymer herein stands for the glass transition temperatureand is well known to be the temperature at which a polymer changes froma glassy, brittle state to a rubbery state. Tg values of polymers may bedetermined experimentally using techniques such as Differential Scanningcalorimetry (DSC) or calculated theoretically using the well-known Foxequation where the Tg (in Kelvin) of a copolymer having “n”copolymerised comonomers is given by the weight fractions “W” and the Tgvalues of the respective homopolymers (in Kelvin) of each comonomer typeaccording to the equation “1/Tg=W₁/Tg₁+W₂/Tg₂+ . . . W_(n)/Tg_(n)”. Thecalculated Tg in Kelvin may be readily converted to ° C.

Preferably the calculated Tg of block [A] is in the range of from 0° C.to 150° C.

Preferably the calculated Tg of block [A] is ≧10° C., most preferably≧20° C. and especially ≧30° C.

Preferably the calculated Tg of block [A] is ≦130° C. and mostpreferably ≦120° C.

Preferably the calculated Tg of polymer P is ≧−10° C., more preferablyin the range of from −5 to 100° C., most preferably −5 to 70° C. andespecially −5 to 50° C.

The weight average molecular weights (Mw) or number average molecularweights (Mn) of the block copolymer may be determined by using gelpermeation chromatography (GPC) with THF as a solvent and polystyrenestandards.

Preferably block [A] has a number average molecular weight in the rangeof from 300 to 10,000 g/mol and more preferably 500 to 5,000 g/mol.

Preferably block [B] has a number average molecular weight in the rangeof from 1,000 to 75,000 g/mol and more preferably 2,000 to 50,000 g/mol.

Preferably block copolymer [A]_(x)[B]_(y) has a weight average molecularweight≦100,000 g/mol, more preferably ≦75,000 g/mol and especially≦50,000 g/mol.

Preferably the composition (block copolymer [A]_(x)[B]_(y) and polymerP) has a weight average molecular weight in the range of from 2,000 to750,000 g/mol, more preferably 10,000 to 500,000 and especially 20,000to 400,000 g/mol.

Preferably block [B] and polymer P are more hydrophobic than block [A].The hydrophobicity of a polymer may be determined by the Hanschparameter. The Hansch parameter for a polymer is calculated using agroup contribution method. The monomer units forming a polymer areassigned a hydrophobicity contribution and the hydrophobicity of thepolymer, the Hansch parameter, is calculated based on the weight averageof the monomers in the polymer as disclosed in for example C. Hansch, P.Maloney, T. Fujita, and R. Muir, Nature, 194. 178-180 (1962). Values ofthe hydrophobicity contributions for several monomers are for example:styrene 4.29, α-methylstyrene 4.7, methyl methacrylate 1.89, butylacrylate 3.19, and acrylic acid −2.52. Therefore a polymer made up ofSTY (20) αMS (20) MMA (20) BA (10) AA (30) has a Hansch value of 1.74.

Preferably the Hansch parameter for block [A] is lower than that forblock [B] and lower than that for polymer P.

Block [A] may have a Hansch parameter less than or equal to 1.7,preferably ≦1.5, more preferably ≦1.2, still more preferably ≦1.0, mostpreferably ≦0.8, especially ≦0.6 and for example ≦0.5.

Block [B] may have a Hansch parameter greater than or equal to 1.0,preferably ≧1.5, more preferably ≧1.7, most preferably ≧2.0 andespecially ≧2.2.

Preferably polymer P has a Hansch parameter greater than or equal to1.7, more preferably ≧2.0 and most preferably ≧2.5.

When in the form of an aqueous dispersion, the block copolymer[A]_(x)[B]_(y) preferably has an acid value from 5 to 150 mgKOH/g andmore preferably 20 to 100 mgKOH/g of block copolymer [A]_(x)[B]_(y),

When in the form of an aqueous dispersion the polymer P has an acidvalue≦50, more preferably ≦15 and especially ≦10 mgKOH/g of polymer P.

The aqueous composition of the invention preferably has an acidvalue≦100, more preferably ≦70 and especially ≦50 mgKOH/g of totalpolymer in the composition.

The RAFT polymerisation process for obtaining block [A] and/or block [B]may be carried out in bulk, in solution, in emulsion, in dispersion orin suspension. Preferably the RAFT polymerisation process for obtainingblock [A] may be performed in solution. Preferably the RAFTpolymerisation process for obtaining block [B] may be performed insolution or by emulsion polymerisation, more preferably in solution.Solution polymerisation is a polymerisation process in which all thereaction components including the monomer(s), initiator and controlagent are dissolved in a non-monomeric liquid solvent at the start ofthe reaction. By non-monomeric is meant a solvent that does not comprisemonomers, in other words that won't react as part of the polymerisation.Usually the solvent is also able to dissolve the polymer or copolymerthat is being formed. By a solvent is meant water, organic solvents ormixtures thereof.

Preferably the block copolymer is prepared according a solutiondispersion polymerization process, which comprises the preparation ofthe block copolymer in solution using a RAFT radical polymerisationprocess and the dispersion of the obtained block copolymer in water.Dispersion of the block copolymer in water can be performed by addingwater to the block copolymer solution or by adding the block copolymersolution to water. Optionally suitable surfactants can be used to aid inthe dispersion process. The block copolymer preferably comprisesacid-functional groups that can be transformed into anionic functionalwater-dispersing groups by addition of a suitable organic or inorganicbase such as for example ammonia, triethylamine or sodium hydroxide.Preferred bases are volatile amines, such as ammonia, or neutralisingagents which decompose without leaving inorganic residues which aresensitive to water in the final dried coating. After the block copolymeris dispersed in water the remaining solvent can optionally be removedfor example under reduced pressure.

Preferred organic solvents include alcohols (such as ethanol,isopropanol, n-butanol, n-propanol, cyclohexanol), esters (such as ethylacetate, propyl acetate, isopropyl acetate, butyl acetate), ketonesolvents (such as acetone, methyl ethyl ketone, methyl isobutyl ketone),and glycols (such as butyl glycol). More preferred organic solventsinclude solvents selected from the group consisting of acetone, ethanol,methyl ethyl ketone, iso-propanol, ethyl acetate, butyl glycol andmixtures thereof. Preferably the solvent is a mixture of water and asuitable organic solvent like an alcohol. Preferably the solvent appliedfor the block copolymer preparation using the solution dispersionpolymerisation process comprises an organic solvent with a low boilingpoint and or a high evaporation rate to allow fast removal of theorganic solvent after the dispersion step under reduced pressure.Examples of such solvents include acetone, ethanol, isopropanol, methylethyl ketone and ethyl acetate.

A process for preparing a block having a gradient composition comprisescontinually introducing a first monomer feed to a reactor, where thefirst monomer feed continually varies in its compositional feed contentduring the continuous introduction by the addition of a different secondmonomer feed to the first monomer feed and polymerising the monomersintroduced into the reactor.

The addition of the second monomer feed to the first monomer feed may bein parallel to the introduction of the first monomer feed to thepolymerisation (i.e. both feeds start and end at the same time).Alternatively the start of monomer feed one to the reactor may precedethe start of the addition of the second monomer feed to the firstmonomer feed, or both monomer feeds may be started simultaneously butthe time taken for the addition of the second monomer feed to the firstmonomer feed may exceed the time taken for the introduction of the firstmonomer feed to the reactor.

A block having a gradient composition may also be obtained by thesimultaneous introduction of a first and a second monomer feed into thereactor where the rate of the introduction of the first monomer feedsvaries with respect to the rate of the introduction of the secondmonomer feed.

The at least two monomer feeds used to prepare the block having agradient composition usually differ in composition. The differencebetween the at least two monomer feeds may be for example a differencein monomer composition, a difference in glass transition temperature(Tg), or simply a variation in the concentration of the respectivemonomers in each monomer feed.

Block [A] and [B] can be prepared in any order.

Polymer P is prepared using a radical emulsion polymerisation process inthe presence of the block copolymer [A]_(x)[B]_(y), where optionally thecontrol agent functional group located at one of the chain ends of theprepared block copolymer [A]_(x)[B]_(y) can be deactivated or removedprior to the preparation of polymer P. General methods for preparingaqueous vinyl polymers are reviewed in the Journal of CoatingTechnology, volume 66, number 839, pages 89 to 105 (1995). The controlagent may optionally be removed before or after dispersion of the blockcopolymer and before or after the polymer preparation. When a RAFT agentis used as control agent the RAFT group can be deactivated or removedvia for example oxidation reactions, radical induced reactions,hydrolysis, or aminolysis. In the case that the control agent functionalgroup is not removed or only partially removed prior to the preparationof polymer P at least part of the polymer P chains will grow onto orbecome covalently attached to at least part of the block copolymerchains.

Preferably the chain end functionality of the block copolymer[A]_(x)[B]_(y) is retained to assist with the covalent bond formationbetween the block copolymer and polymer P. The chain end functionalityof the block copolymer may be a RAFT group (—S—C(═S)—) or a thiol (—SH)group or any other group derived from the RAFT control agent that canprovide covalent bond formation between the block copolymer and polymerP.

Preferably at least 20 wt % of polymer P is covalently bonded to theblock copolymer.

In an embodiment of the invention there is provided an aqueouscomposition comprising a block copolymer and a polymer obtainedaccording to the process of the invention. The aqueous composition maycontain free block copolymer [A]_(x)[B]_(y) and free polymer P.Preferably, the block copolymer [A]_(x)[B]_(y) and polymer P arepartially grafted by means of covalent bond(s) between the blockcopolymer [A]_(x)[B]_(y) and polymer P.

In another embodiment of the invention there is provided a process forpreparing a composition according to the invention wherein said methodcomprises the following steps:

-   -   1. synthesis in a solvent by means of a RAFT radical        polymerisation process of a first block [A] followed by the        polymerisation of at least a second block [B]. The order of        preparation of [A] and [B] can also be reversed;    -   2. optional removal of the control agent before, during or after        dispersing the block copolymer [A]_(x)[B]_(y) in water;    -   3. optional removal of the solvent from block copolymer        [A]_(x)[B]_(y);    -   4. dispersion of the block copolymer [A]_(x)[B]_(y) in water        optionally containing monomers, by adding either water to the        block copolymer [A]_(x)[B]_(y) or adding the block copolymer        [A]_(x)[B]_(y) to water, optionally using surfactants,        preferably by addition of a base;    -   5. optional removal of solvent from the block copolymer        [A]_(x)[B]_(y) dispersion (if solvent is still present from step        4.);    -   6. performing an emulsion polymerisation process of monomers in        the presence of the block copolymer [A]_(x)[B]_(y) dispersion        prepared in step 4 and or step 5 to obtain polymer P.

Alternatively after step 1 the solvent is removed by a suitable methodto get a solid, which solid can be afterwards dispersed into water.

Furthermore the polymerisation process to make the block copolymer orthe polymer may be carried out as either a batch, semi-batch or acontinuous process. When the polymerisation process for the blockcopolymer is carried out in the batch mode, the reactor is typicallycharged with control agent and monomer. To the mixture is then added thedesired amount of initiator. The mixture is then heated for the requiredreaction time. In a batch process, the reaction may be run underpressure to avoid monomer reflux.

Semi-batch operation typically involves the continuous or step-wiseaddition of monomer(s) (and/or other ingredients) during polymerisation,and is often applied in copolymerisations to minimize copolymercomposition drift in case monomer reactivities are very different. Ifthe polymerisation process for the block copolymer is to be carried outas a semi-batch process, the reaction is typically carried out asfollows: the reactor is charged with a polymerisation medium, typicallyan organic solvent, the control agent, and optionally (part of) theinitiator. Into a separate vessel are placed the monomer(s) andoptionally polymerisation medium and initiator. For safety reasons theinitiator can also be added via another separate vessel. Thepolymerisation medium in the reactor is heated and stirred while themonomer(s) and initiator are step-wise or gradually introduced. The rateof monomer and/or initiator addition is determined largely by thequantity of solution and/or the rate of polymerisation. When theadditions are completed, heating may be continued for an additionalperiod of time with or without additional initiator to reduce unreactedmonomer levels.

Furthermore after preparation of a first block, the prepared block canbe purified from residual monomers and subsequently used for thepolymerisation of a second monomer composition as a second block or thesecond monomer composition can be polymerised directly after thepreparation of first block is completed. In this case at least 80 wt %,preferably at least 90 wt %, most preferred at least 95 wt % of thefirst block monomer composition is reacted before the second monomercomposition is reacted. The second block can contain up to 20 wt %(preferably 10 wt % or less) of the first monomer composition.

A free-radical polymerisation of ethylenically unsaturated monomers tomake either the block copolymer and or the polymer will require the useof a source of free radicals (i.e. an initiator) to initiate thepolymerisation. Suitable free-radical-yielding initiators includeinorganic peroxides such as K, Na or ammonium persulphate, hydrogenperoxide, or percarbonates; organic peroxides, such as acyl peroxidesincluding for example benzoyl peroxide, alkyl hydroperoxides such ast-butyl hydroperoxide and cumene hydroperoxide; dialkyl peroxides suchas di-t-butyl peroxide; peroxy esters such as t-butyl perbenzoate;mixtures may also be used. The peroxy compounds are in some casesadvantageously used in combination with suitable reducing agents (redoxsystems) such as iso-ascorbic acid. Metal compounds such as Fe.EDTA(ethylene diamine tetracetic acid) may also be usefully employed as partof the redox initiator system. Azo functional initiators such as2,2′-azobis(isobutyronitrile) (AIBN),2,2′-azobis(2-methyl-butyronitrile) (AMBN) and4,4′-azobis(4-cyanovaleric acid) may also be used. The amount ofinitiator or initiator system to use is conventional. For thepreparation of the block copolymer preferably the molar amount ofinitiator does not exceed the molar amount of control agent that isapplied. A further amount of initiator may optionally be added at theend of the polymerisation process to assist the removal of any residualethylenically unsaturated monomers.

A chain transfer agent may be added to control the molecular weight ofthe polymer. Suitable chain transfer agents include mercaptans such asn-dodecylmercaptan, n-octylmercaptan, t-dodecylmercaptan,mercaptoethanol, iso-octyl thioglycolate, C₂ to C₈ mercapto carboxylicacids and esters thereof such as 3-mercaptopropionic acid and2-mercaptopropionic acid; and halogenated hydrocarbons such as carbontetrabromide and bromotrichloromethane. Preferably no chain transferagent is added during the preparation of the block copolymer.

Surfactants can be utilised in order to assist in the dispersion of theblock copolymer or polymer, and or in the emulsification of the monomersin water (even if self-dispersible). Suitable surfactants include butare not limited to conventional anionic, cationic and/or nonionicsurfactants and mixtures thereof such as Na, K and NH₄ salts ofdialkylsulphosuccinates, Na, K and NH₄ salts of alkyl sulphonic acids,Na, K and NH₄ alkyl sulphates, ethoxylated fatty acids and/or fattyamides, and Na, K and NH₄ salts of fatty acids such as Na stearate andNa oleate. Other anionic surfactants include alkyl or (alk)aryl groupslinked to sulphonic acid groups, sulphuric acid half ester groups(linked in turn to polyglycol ether groups), phosphonic acid groups orcarboxylic acid groups. Cationic surfactants include alkyl or (alk)arylgroups linked to quaternary ammonium salt groups. Nonionic surfactantsinclude polyglycol ether compounds and preferably polyethylene oxidecompounds as disclosed in “Nonionic surfactants—Physical chemistry”edited by M. J. Schick, M. Decker 1987.

If monomers bearing crosslinking functional groups are present, thencrosslinking may be introduced by combining the block copolymer obtainedby the process of the invention with a separate crosslinker to provideeither a self-crosslinking system (with a long potlife, triggered by forinstance a change in temperature or pH or the evaporation of one of theingredients in the overall system, like a solvent or water), or a twopack system.

A separate crosslinking agent is preferably selected from groupconsisting of polyhydrazides (including dihydrazides such as adipic aciddihydrazide), polyisocyanates, carbodiimides, polyaziridines, epoxies,melamine resins and mixtures thereof.

The composition obtained by the process of the invention can be in theform of a solid, a solution or as an aqueous dispersion. Most preferablythe composition is used in an aqueous composition.

Furthermore the composition obtained by the process of the invention isparticularly suitable for use in coating applications in which it mayprovide a key part of coating compositions or formulations. Thecomposition may be used in compositions suitable for applications suchas adhesives, coatings, films, cosmetics, inks. Such coatingcompositions can be pigmented or unpigmented. Such coating compositionsmay be applied to a variety of plastic substrates by any conventionalmethod including brushing, dipping, flow coating, spraying, flexoprinting, gravure printing any other graphic arts application methodsand the like. The aqueous carrier medium is removed by natural drying oraccelerated drying (by applying heat) to form a coating.

The coating composition can be applied to a broad variety of plasticsubstrates, including for example polyolefins such as polypropylene (PP)(treated and untreated) and polyethylene (PE), polyamide, polycarbonate(PC), polyethyleneterepthalate (PET), polymethyl methacrylate (PMMA),polystyrene (PS), acrylonitrile/butadiene/styrene copolymer (ABS),polytetrafluoroethylene (PTFE)) and polyvinyl chloride (PVC).

The polyolefins comprise in particular olefin polymers, especiallypolymers of olefins containing 2 to 8, and preferably 2 to 5 and mostpreferably 3 carbon atoms. The polyolefins include, without beinglimited thereto, polyethylene, polypropylene, polybutenes, polypentenes,and copolymers of these with small amounts of other monomers with whichthey are copolymerizable. Included are such copolymers containing atleast 85% by weight of olefin units.

Of greatest importance is the group of polyolefins known as “untreatedpolyolefins” and particularly “untreated polypropylene”. Untreatedpolyolefin surfaces are difficult to bond as well as to wet. Thedifficulty is often ascribed to the non-polar and hydrophobic nature ofthe purely hydrocarbon surface present on these materials. Polypropylenehas been singled out as being especially difficult and it has beensuggested that the reason for the particular difficulty in bonding tountreated polypropylene is that the surface consists essentially ofmethyl groups. Although treatment of polyolefin substrates such ascorona treatment of polypropylene films or flame treatment ofpolypropylene articles is commonly applied to improve wetting andcoating adhesion, it is often found that these treatments areinsufficient or incomplete and therefore do not give the desiredadhesion performance. Furthermore, treated polypropylene films forexample show a decrease in surface tension over time upon storage, andmay therefore require an additional treatment step shortly beforeapplication of the coating to prevent serious issues in wetting andcoating adhesion. The coating composition of the invention howeverprovides good adhesion to both treated and untreated polypropylene, andcan therefore advantageously be applied to both untreated polypropylenesubstrates and to treated or partly treated polypropylene substrates. Itmay also be applied to treated or untreated substrates made from blendsof polypropylene with other polymers such aspoly(ethylene/propylene/diene), polyphenylene sulphide, polyphenyleneoxide etc. The substrate may be in the form of a moulded or extrudedarticle or film. Polypropylene films include oriented polypropylene(OPP) and biaxially oriented polypropylene (BOPP) films, which may betreated or untreated.

Polyolefins like PE and PP and fluorocarbons (likepolytetrafluoroethylene (PTFE)) are considered as very hydrophobicplastic substrates. Adhesion to such very hydrophobic plastics typicallyrequires the use of blocks (preferably long blocks) of hydrophobicmonomers that can mix and/or entangle and/or co-crystallise with thepolymer chains from the plastic substrate surface (often in combinationwith a co-solvent and/or elevated drying temperature to mobilise thechains). Preferably the monomers used in the block copolymer arecompatible with the monomers present in the plastic. For example if apolypropylene substrate is used it is advantageous to use anisobornyl(meth)acrylate rich block to improve adhesion to the substrate.

Preferably the plastic substrate is a hydrophobic plastic. Examples ofhydrophobic plastic substrates include (non-modified or untreated)polypropylene (PP), polyethylene (PE), polytetrafluoroethylene (PTFE)and polystyrene (PS). Most preferably the substrate is untreated PP.

In a preferred embodiment the aqueous coating composition of theinvention is suitable for coating polyolefins, more preferablypropylene, most preferably untreated polypropylene.

Optionally in one embodiment of the invention the composition obtainedor obtainable by the process of the invention may comprise one or moresolventborne or waterborne adhesion promoting resins such as chlorinatedpolyolefin (CPO) or chlorine-free modified polyolefin resins. Suchresins may advantageously be used in amounts ranging from 1 to 40 wt %preferably 3 to 25 wt % based on total binder solids for furtherincreasing the overall level of coating adhesion to very hydrophobicplastics such as polypropylene. Preferred examples of polyolefinadhesion promoters comprise waterborne chlorinated polyolefins (such asthose available commercially from Nippon Paper Chemicals under the tradedesignations Superchlon E-723, E-673, and/or E-503),and theenvironmentally more preferred waterborne non-chlorinated (acrylicmodified) polyolefins (such as that available commerically from Eastmanunder the trade name Advantis 510W and/or those available commerciallyfrom Nippon Paper Chemicals under the trade designations Auroren AE-201and/or AE-301).

For plastic adhesion a co-solvent may be needed to swell the surface ofthe plastic to allow a certain degree of chain interdiffusion.

Suitable organic co-solvents which may be added during the process orafter the process during formulation steps are well known in the art andinclude xylene, toluene, methyl ethyl ketone, acetone, ethanol,isopropanol, ethyl acetate, butyl acetate, diethylene glycol, ethylenediglycol, butyl glycol, butyl diglycol, dipropylene glycol methyl ether,propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, and1-methyl-2-pyrrolidinone.

Preferably the aqueous composition comprises ≦50 wt %, more preferablyfrom ≦40 wt % and most preferably from ≦35 wt % of organic co-solvent byweight of total polymer.

Preferably only a low concentration of aromatic solvent is added.Preferably less than 10 wt %, more preferably less than 5 wt % and mostpreferred less than 2 wt % of aromatic solvent by weight of totalpolymer is added.

The solids content of the aqueous composition is preferably from 20 to60 wt %, and most preferably from 30 to 50 wt %.

If desired the composition obtained by the process of the invention canbe used in combination with other polymer compositions which are notaccording to the invention.

In another embodiment there is provided an aqueous emulsion according tothe invention additionally comprising a polymer Q, wherein the solidscontent of the blockcopolymer—polymer P together is ≧1 wt % and ≦35 wt %based on total solids content of blockcopolymer—polymer P and polymer Qtogether. Preferably polymer Q is an acrylic, urethane,urethane-acrylic, alkyd, alkyd-acrylic or another type of polymer.

In a preferred embodiment there is provided a blend of an aqueouspolymer Q dispersion comprising an acrylic, urethane, urethane-acrylic,alkyd, alkyd-acrylic or another type of polymer Q with the aqueousemulsion of the invention. The advantage of such blending is that theoverall performance properties of the aqueous polymer dispersion(coating) are retained, and additionally the aqueous emulsion of theinvention provides improved adhesion of the coating to plasticsubstrates, and in particular hydrophobic plastic substrates such aspolypropylene.

Preferably the solids content of the aqueous emulsion prepared by theprocess of the invention added to the aqueous polymer Q dispersionamounts ≦35 wt % on total solids content of the blend and morepreferably ≦25 wt %. Preferably the solids content of the aqueousemulsion prepared by the process of the invention added to the aqueouspolymer Q dispersion amounts ≧1 wt % on total solids content of theblend and more preferably ≧5 wt %.

Preferably the polymer Q dispersion that is added to the aqueousemulsion prepared by the process of the invention is an aqueous acrylicpolymer dispersion.

Preferably the particle size of the polymer Q dispersion that is blendedwith the aqueous emulsion prepared by the process of the invention ofthe invention is in the range of from 50 to 400 nm, preferably ≧100 nm.Preferably the particle size of the aqueous emulsion according to theinvention is ≦100 nm.

In addition to the block copolymers and other ingredients alreadydescribed herein, a coating composition of the invention may alsocontain further conventional ingredients such as: carrier medium,pigments, dyes, emulsifiers, surfactants, plasticisers, thickeners, heatstabilisers, levelling agents, anti-cratering agents, fillers,sedimentation inhibitors, UV absorbers, antioxidants, dispersants,reactive diluents, waxes, neutralising agents, adhesion promoters,defoamers, co-solvents, wetting agents, fire retardants and the like,any combinations thereof and/or any mixtures thereof. The ingredientsmay be introduced at any stage of the production process orsubsequently.

The coating composition of the invention may be applied to a variety ofplastic substrates by any conventional method including brushing,dipping, flow coating, spraying, and the like. A carrier medium ifpresent may removed by natural drying or accelerated drying (e.g. byapplying heat) to form a coating.

An aspect of the invention provides a coating composition and/or polymerobtained and/or obtainable by a process of the invention

An aspect of the invention provides a coating composition obtainedand/or obtainable by a process of the invention

Another aspect of the invention provides a mixture of i) block copolymercomprising at least blocks [A]_(x)[B]_(y), and ii) polymer P; where saidmixture is obtained and/or obtainable by a process of the invention

Yet another aspect of the invention provides a blockcopolymer-polymercomprising as components thereof i) block copolymer comprising at leastblocks [A]_(x)[B]_(y) and ii) polymer P; said blockcopolymer-polymerobtained and/or obtainable by a process of the invention.

A further aspect of the invention provides a coating obtained and/orobtainable from a coating composition, mixture and/or blockcopolymer-polymer of the invention.

Another aspect of the invention provides a substrate and/or articlecoated with a coating of the invention.

A still other aspect of the invention provides a method of coating asubstrate and/or article comprising the steps of i) applying a coatingcomposition, mixture and/or block copolymer-polymer of the invention tothe substrate and/or article; ii) drying the substrate and/or article toform a coating thereon.

A further aspect of the invention provides use of a coating composition,mixture, block copolymer-polymer, substrate and/or article of theinvention to coat a substrate and/or article.

A yet other aspect of the invention provides for a coated substrateand/or article obtained and/or obtainable by the method of coating ofthe invention.

A further aspect of the invention provides use of a coating composition,mixture, block copolymer-polymer, substrate and/or article of theinvention in at least one of the applications descibed herein.

A still yet other aspect of the invention provides a method ofmanufacture of a coating composition, mixture, block copolymer-polymer,substrate and/or article of the invention for the purpose being used inat least one of the applications descibed herein.

The terms ‘effective’, ‘acceptable’ ‘active’ and/or ‘suitable’ (forexample with reference to any process, use, method, application,preparation, product, material, formulation, compound, monomer, blockcopolymer, polymer precursor, and/or polymers of the present inventionand/or described herein as appropriate) will be understood to refer tothose features of the invention which if used in the correct mannerprovide the required properties to that which they are added and/orincorporated to be of utility as described herein. Such utility may bedirect for example where a material has the required properties for theaforementioned uses and/or indirect for example where a material has useas a synthetic intermediate and/or diagnostic tool in preparing othermaterials of direct utility. As used herein these terms also denote thata functional group is compatible with producing effective, acceptable,active and/or suitable end products.

Preferably the utility, end use and/or applications for the polymers,compostions, substrates and/or articles of the present invention may beselected from at least one of the following non-limiting list, anycombinations and/or mixtures thereof (some of which may overlap):

-   -   coatings for plastic substrates and/or foams;    -   coatings for surfaces having low surface energy;    -   coatings for hydrophobic substrates such as for example        polyolefins;    -   coatings for polyolefins, such as polypropylene (PP), for        example PP articles and oriented PP (OPP) and/or biaxial OPP        (BOPP) films, either treated or preferably untreated;    -   coatings for vehicles such as interior and/or exterior        automotive coatings;    -   coatings for consumer electronic articles, preferably the        plastic parts thereof;    -   coatings for furniture and/or household articles, preferably the        plastic parts thereof;    -   coatings for biomedical articles, preferably the plastic parts        thereof such as catheters.

Many other variations embodiments of the invention will be apparent tothose skilled in the art and such variations are contemplated within thebroad scope of the present invention.

Further aspects of the invention and preferred features thereof aregiven in the claims herein.

EXAMPLES

The present invention is now illustrated by reference to the followingnon-limiting examples. Unless otherwise specified, all parts,percentages and ratios are on a weight basis. Molecular weights weredetermined by GPC using polystyrene standards and THF as eluent.

The prefixes Comp or C before an example denotes that it is comparative.The term “working” means that the example is according to the invention.The term “non-working” means that it is not according to the invention(i.e. comparative).

Various registered trademarks, other designations and/or abbreviationsare used herein to denote some of ingredients used to prepare polymersand compositions of the invention. These are identified below bychemical name and/or trade-name and optionally their manufacturer orsupplier from whom they are available commercially. However where achemical name and/or supplier of a material described herein is notgiven it may easily be found for example in reference literature wellknown to those skilled in the art: such as: ‘McCutcheon's Emulsifiersand Detergents’, Rock Road, Glen Rock, N.J. 07452-1700, USA, 1997 and/orHawley's Condensed Chemical Dictionary (14th Edition) by Lewis, RichardJ., Sr.; John Wiley & Sons. In the examples, the following abbreviationsand terms are specified:

-   DP=average degree of polymerization-   AA=acrylic acid-   BA=butyl acrylate-   MMA=methyl methacrylate-   BMA=butyl methacrylate-   iBOA=isobornyl acrylate-   xanthate1=O-ethyl-S-(1-methoxycarbonyl)ethyl dithiocarbonate    (Rhodixan A1, provided by Rhodia Chimie)-   MEK=methyl ethyl ketone-   SLS=sodium lauryl sulfate-   APS=ammonium persulfate

Molecular weights were determined by GPC relative to polystyrenestandards.

An overview of the Examples and the Comparative Examples is given inTable 1.

TABLE 1 Block copolymer (BC) [DP]/ BC/RC wt % Experiment Randomcopolymer (RC) [DP] Polymer P (Tg ° C.) on total solids Example 1 BC1 =AA-iBOA [20-50] BMA/BA (0° C.) 26% Example 2 BC1 = AA-iBOA [20-50]BMA/BA (0° C.) 16% Example 3 BC1 = AA-iBOA [20-50] BMA/BA (10° C.) 26%Example 4 BC2 = AA-iBOA [50-100] BMA/BA (0° C.) 33% Comparative RC1 =AA/iBOA [20/50]; BMA/BA (0° C.) 16% Example 1a 12 wt % AA ComparativeRC2 = AA/iBOA [33/46]; BMA/BA (0° C.) 16% Example 1b 20 wt % AAComparative RC3 = AA/iBOA [49/40]; BMA/BA (0° C.) 16% Example 1c 30 wt %AA Comparative BC3 = AA-BA [20-50] BMA/BA (10° C.) 16% Example 2Comparative None MMA/BA/iBOA/AA — Example 3 (21° C.) Comparative NoneBMA/BA/iBOA/AA — Example 4 (12° C.) Comparative None BMA/BA/iBOA/AA —Example 5 (25° C.)

Block Copolymer 1

Synthesis of a [A]_(x)-[B]_(y) Block Copolymer where Block [A] is Basedon AA and x=20 and Block [B] is Based on iBOA with y=50

Block [A]:

170 gram of ethanol and 28 gram (0.14 mol) of xanthate 1 were added to a1 L three-necked glass flask equipped with condenser cooler, temperaturemeasuring probe and mechanical stirring device. The reaction mixture wasdegassed by purging with nitrogen at room temperature for 15 minuteswhile stirring. The temperature was raised to 75° C. and 10wt % of amonomer feed mixture of 197 gram (2.74 mol) of AA and 228 gram ofethanol was added to the reaction mixture. Then a mixture of 2.3 gram(approximately 6 mmol) of 4,4′-azobis(4-cyanovaleric acid) (Aldrich,75+%) and 25 gram of ethanol was added. After 15 minutes at 70° C. thegradual addition was started of the remaining 90wt % of the AA/ethanolmixture. The addition lasted 4 hours under a weak nitrogen stream and ata controlled temperature of 70° C., after which the mixture was kept for7 hours at 70° C. The reaction mixture was then cooled to 20° C. and asample was withdrawn for further analysis. The conversion of AA asdetermined with gas chromatography was found to be 96% and the solidslevel was experimentally determined at 37.5%. GPC analysis of the finalproduct resulted in the following values: Mn=1905 g/mol, PDI(=Mw/Mn)=1.30.

Block [B]:

237 gram of the block [A] reaction mixture, corresponding toapproximately 54 mmol of precursor block [A] based on a solids level of37.5% and a theoretical molecular weight of 1650 g/mol, and 60 gram ofMEK were added to a 2 L three-necked glass flask equipped with condensercooler, temperature measuring probe and mechanical stirring device. Thereaction mixture was degassed by purging with nitrogen at roomtemperature for 15 minutes while stirring. The temperature was raised to70° C. and 10 wt % of a monomer feed mixture of 562 gram (2.70 mol) ofiBOA and 425 gram of MEK was added to the reaction mixture. Then amixture of 3.0 gram (approximately 8 mmol) of 4,4′-azobis(4-cyanovalericacid) (Aldrich, 75+%) and 20 gram of MEK was added to the reactionmixture. After 15 minutes at 70° C. the gradual addition was started ofthe remaining 90 wt % of the iBOA/MEK mixture. The addition lasted 4hours under a weak nitrogen stream and at a controlled temperature of70° C., after which the mixture was kept for about 10 hours at 70° C.The reaction mixture was then cooled to 20° C. and a sample waswithdrawn for further analysis. The conversion of iBOA as determinedwith gas chromatography was found to be 97%. Theoretical solids levelwas 50%. GPC analysis of the final [A]-[B] block copolymer productresulted in the following values: Mn=4870 g/mol, PDI (=Mw/Mn)=2.25.

Block Copolymer 2

Synthesis of a [A]_(x)-[B]_(y) Block Copolymer where Block [A] is Basedon AA and x=50 and Block [B] is Based on iBOA with y=100

Block [A]:

189 gram of ethanol and 10.6 gram (51 mmol) of xanthate 1 were added toa 1 L three-necked glass flask equipped with condenser cooler,temperature measuring probe and mechanical stirring device. The reactionmixture was degassed by purging with nitrogen at room temperature for 15minutes while stirring. The temperature was raised to 75° C. and 5 wt %of a monomer feed mixture of 184 gram (2.55 mol) of AA and 241 gram ofethanol was added to the reaction mixture. Then a mixture of 0.8 gram(approximately 2.2 mmol) of 4,4′-azobis(4-cyanovaleric acid) (Aldrich,75+%) and 25 gram of ethanol was added. After 15 minutes at 70° C. thegradual addition was started of the remaining 95 wt % of the AA/ethanolmixture. The addition lasted 4 hours under a weak nitrogen stream and ata controlled temperature of 70° C., after which the mixture was kept for7 hours at 70° C. The reaction mixture was then cooled to 20° C. and asample was withdrawn for further analysis. The conversion of AA asdetermined with gas chromatography was found to be 94% and the solidslevel was experimentally determined at 33.1%. GPC analysis of the finalproduct resulted in the following values: Mn=3040 g/mol, PDI(=Mw/Mn)=1.47.

Block [B]:

298 gram of the block [A] reaction mixture, corresponding toapproximately 26 mmol of precursor block [A] based on a solids level of33.1% and a theoretical molecular weight of 3810 g/mol, was added to a 2L three-necked glass flask equipped with condenser cooler, temperaturemeasuring probe and mechanical stirring device. The reaction mixture wasdegassed by purging with nitrogen at room temperature for 15 minuteswhile stirring. The temperature was raised to 70° C. and 10 wt % of amonomer feed mixture of 540 gram (2.60 mol) of iBOA and 500 gram of MEKwas added to the reaction mixture. Then a mixture of 1.8 gram(approximately 5 mmol) of 4,4′-azobis(4-cyanovaleric acid) (Aldrich,75+%) and 20 gram of MEK was added to the reaction mixture. After 15minutes at 70° C. the gradual addition was started of the remaining 90wt % of the iBOA/MEK mixture. The addition lasted 4 hours under a weaknitrogen stream and at a controlled temperature of 70° C., after whichthe mixture was kept for about 10 hours at 70° C. The reaction mixturewas then cooled to 20° C., and 140 gram MEK was added to reduce theviscosity of the mixture. The conversion of iBOA as determined with gaschromatography was found to be 95%. Theoretical solids level was 45%.GPC analysis of the final [A]-[B] block copolymer product resulted inthe following values: Mn=5890 g/mol, PDI (=Mw/Mn)=2.66.

Block Copolymer 3

Synthesis of a [A]_(x)-[B]_(y) Block Copolymer where Block [A] is Basedon AA and x=20 and Block [B] is Based on BA with y=50

The block [A] reaction mixture for block copolymer 3 was preparedaccording a similar recipe and procedure as described for blockcopolymer 1 (data for block [A] from GPC analysis: Mn=2190 g/mol, PDI(=Mw/Mn)=1.25). For the preparation of block [B] of block copolymer 3,164.7 gram of the block [A] reaction mixture, corresponding toapproximately 40 mmol of precursor block [A] based on a solids level of40.1% and a theoretical molecular weight of 1650 g/mol, and 14 gram ofMEK were added to a 1 L three-necked glass flask equipped with stirrer,condenser cooler and temperature measuring probe. The reaction mixturewas degassed by purging with nitrogen at room temperature for 15 minuteswhile stirring. The temperature was raised to 75° C. and 10 wt % of amonomer feed mixture of 256.8 gram (2.0 mol) of BA and 202.4 gram of MEKwas added to the reaction mixture. Then a mixture of 2.24 gram(approximately 6 mmol) of 4,4′-azobis(4-cyanovaleric acid) (Aldrich,75+%) and 10 gram of MEK was added. After 15 minutes at 70° C. thegradual addition was started of the remaining 90 wt % of the BA/MEKmixture. The addition lasted 4 hours under a weak nitrogen stream and ata controlled temperature of 70° C., after which the mixture was kept for6 hours at 70° C. The reaction mixture was then cooled to 20° C. and asample was withdrawn for further analysis. The conversion of BA asdetermined with gas chromatography was found to be 96% and the solidslevel was experimentally determined at 49.8%. GPC analysis of the final[A]-[B] block copolymer product resulted in the following values:Mn=6610 g/mol, PDI (=Mw/Mn)=1.59.

Random Copolymers of AA and iBOA (RC1; RC2; RC3)Synthesis of Random Copolymer RC1 of AA and iBOA with the Same OverallComposition as Block Copolymer 1 (wt % AA=12%; DP AA=20 and DP iBOA=50)

130 gram of MEK and 6.0 gram (29 mmol) of xanthate 1 were added to a 1 Lthree-necked glass flask equipped with condenser cooler, temperaturemeasuring probe and mechanical stirring device. The reaction mixture wasdegassed by purging with nitrogen at room temperature for 15 minuteswhile stirring. The temperature was raised to 75° C. and 10 wt % of amonomer feed mixture of 41.8 gram (0.58 mol) of AA, 302.0 gram (1.45mol) of iBOA, and 200 gram MEK was added to the reaction mixture. Then amixture of 2.20 gram (approximately 6 mmol) of4,4′-azobis(4-cyanovaleric acid) (Aldrich, 75+%) and 23 gram of ethanolwas added. After 15 minutes at 70° C. the gradual addition was startedof the remaining 90wt % of the AA/iBOA/MEK mixture. The addition lasted5 hours under a weak nitrogen stream and at a controlled temperature of70° C., after which the mixture was kept for 5 hours at 70° C. Thereaction mixture was then cooled to 20° C. and a sample was withdrawnfor further analysis.

The synthesis of random copolymer RC2 (20 wt % AA; DP AA=33 and DPiBOA=46) and random copolymer RC3 (30 wt % AA; DP AA=49 and DP iBOA=40)was performed according the same recipe and procedure as describedabove, where the ratio of AA and iBOA in the monomer feed mixture wasadjusted to obtain the desired degree of polymerization.

The theoretical solids level of RC1, RC2 and RC3 was 50%. GPC analysisof the final random copolymers resulted in the following values: RC1Mn=5655 g/mol and PDI=2.03; RC2 Mn=6515 g/mol and PDI=2.01; RC3 Mn=6120g/mol and PDI=2.14.

Preparation of an Aqueous Dispersion of Block Copolymer 1

53.3 gram of triethylamine was added to 660 gram of block copolymer 1 at20° C. whilst stirring. To the obtained mixture an amount of 1320 gramdemineralized water was slowly added under stirring, resulting in theformation of a stable aqueous dispersion. After removal of residual MEKfrom the dispersion under reduced pressure the pH was measured at 8.1and the final solids level was experimentally determined at 24.3%. Theparticle size of the dispersion as determined with light scattering was40 nm.

Preparation of an Aqueous Dispersion of Block Copolymer 2

38.7 gram of triethylamine was added to 460 gram of block copolymer 2 at20° C. whilst stirring. To the obtained mixture an amount of 828 gramdemineralized water was slowly added under stirring, resulting in theformation of a stable aqueous dispersion. After removal of residual MEKfrom the dispersion under reduced pressure the pH was measured at 7.8and the final solids level was experimentally determined at 22.6%. Theparticle size of the dispersion as determined with light scattering was117 nm.

Preparation of an Aqueous Dispersion of Block Copolymer 3

35.8 gram of triethylamine was added to 401 gram of block copolymer 3 at20° C. whilst stirring. To the obtained mixture an amount of 800 gramdemineralized water was slowly added under stirring, resulting in theformation of a stable aqueous dispersion. After removal of residual MEKfrom the dispersion under reduced pressure the pH was measured at 7.0and the final solids level was experimentally determined at 22.9%. Theparticle size of the dispersion as determined with light scattering was32 nm.

Preparation of an Aqueous Dispersion of Random Copolymers RC1, RC2 andRC3

The preparation of an aqueous dispersion of random copolymer RC1 wasperformed according a similar recipe and procedure as applied for blockcopolymer 1. For RC2 and RC3 the amount of triethylamine was adjusted toequal molar ratio to the number of carboxylic acid groups. After removalof residual MEK from the dispersion under reduced pressure the pH forRC1, RC2 and RC3 was measured at 8.5, 8.3 and 7.7, respectively. Thefinal solids level for RC1, RC2 and RC3 was experimentally determined at22.4%, 21.9% and 25.7%, respectively. The dispersions of RC1 and RC2were of relatively poor quality; analysis with light scattering resultedin a very broad particle size distribution (polydispersity>0.95), withan average particle size of about 200 and 600 nm, respectively. Thedispersion of RC3 was a stable clear aqueous solution (no measurableparticle size).

Example 1 Synthesis of a BMA/BA Emulsion Polymer in the Presence ofBlock Copolymer 1

75 gram of demineralized water and 185.6 gram of the aqueous dispersionof block copolymer 1 prepared above (24.3% in water) were added to a 1 Lthree-necked glass flask equipped with stirrer, condenser cooler andtemperature measuring probe. The reaction mixture was heated whilestirring to 65° C. under nitrogen atmosphere. Then a mixture of 35.3gram BMA and 9.8 gram BA was added. After 20 minutes mixing at 65° C. aninitiator mixture of 0.2 gram APS and 20 gram demineralized water, setat pH=8 with triethylamine, was added. The reaction mixture was thenheated to 85° C. After 10 minutes at 85° C. the gradual addition wasstarted of an initiator feed mixture of 0.2 gram APS and 18 gramdemineralized water (set at pH=8 with triethylamine), and apre-emulsified monomer feed mixture of 55 gram demineralized water, 0.2gram SLS (30wt % in water), 65.6 gram BMA and 18.2 gram BA. Bothmixtures were added as parallel feeds to the reaction mixture over atime period of 2.5 hours. During the reaction the pH of the reactionmixture was kept above 7.0. At the end of the monomer and initiator feedthe reaction mixture was kept for 30 minutes at 85° C. A post reactionwith tert-butyl hydroperoxide and isoascorbic acid was performed toreact any residual monomer. The resultant emulsion was then cooled toroom temperature and the pH was adjusted with triethylamine to 8.0.

Examples 2 and 3 were prepared using a similar recipe and procedure asapplied for Example 1, but now either the amount of block copolymer wasvaried (Example 2) or the Tg of the emulsion polymer was varied bychanging the BMA/BA wt ratio (Example 3).

Example 4 was prepared using a similar recipe and procedure as appliedfor Example 1, but now the dispersion of block copolymer 2 was appliedat a level of 33 wt % on total solids.

Comparative Examples 1a, 1b and 1c Synthesis of a BMA/BA EmulsionPolymer in the Presence of Random Copolymer RC1, RC2, or RC3

The preparation of the comparative examples 1a, 1b and 1c based on RC1,RC2 and RC3, respectively, was performed using the same recipe andprocedure as applied for Example 2, but now the aqueous dispersions ofeither random copolymer RC1, RC2 or RC3 was applied, each at a level of16 wt % on total solids.

It was found that Comparative Examples 1a and 1b could not be preparedas the synthesis of the emulsion polymers based on RC1 and RC2 resultedin excessive amounts of fouling and sediment formation. These resultsdemonstrate that the random copolymers RC1 (12 wt % AA) and RC2 (20 wt %AA) exhibit very poor stabilization properties, especially when comparedto the respective block copolymers. The synthesis of the emulsionpolymer based on RC3 (30 wt % AA), Comparative Example 1c, gaverelatively low fouling and sediment formation and resulted in a stablelatex that was found to be acceptable for further testing.

Comparative Example 2 Synthesis of a BMA/BA Emulsion Polymer in thePresence of Block Copolymer 3

Comparative Example 2 was prepared using a similar recipe and procedureas applied for Example 3, but now the dispersion of block copolymer 3was applied at a level of 16 wt % on total solids.

Comparative Example 3 Synthesis of a MMA/BA/iBOA/AA Emulsion Polymer

310 gram of demineralized water and 10.9 gram of SLS (30wt % in water)were added to a 2 L three-necked glass flask equipped with stirrer,condenser cooler and temperature measuring probe. The reaction mixturewas heated while stirring to 75° C. under nitrogen atmosphere. Then 10wt % was added of a pre-emulsified monomer mixture consisting of intotal 165 gram demineralized water, 5.5 gram SLS (30 wt % in water),176.6 gram MMA, 151.8 gram BA, 56.4 gram iBOA, and 7.7 gram AA. Thereaction mixture was further heated to 75° C. and then a mixture of 0.3gram APS and 5.3 gram demineralized water was added. The reactionmixture was then heated to 85° C. and kept at this temperature for 15minutes. An initiator feed mixture of 0.69 gram APS and 68.3 gramdemineralized water and the remaining 90 wt % of the pre-emulsifiedmonomer feed were then gradually added as parallel feeds to the reactionmixture over a time period of 3 hours. The reaction mixture was thenkept for 30 minutes at 85° C. A post reaction with tert-butylhydroperoxide and isoascorbic acid was performed to react any residualmonomer. The resultant emulsion was then cooled to room temperature. ThepH of the latex was adjusted to 8.0 by addition of ammonia.

Comparative Example 4 Synthesis of a BMA/BA/iBOA/AA Emulsion Polymer

606 gram of demineralized water and 17.1 gram of SLS (30 wt % in water)were added to a 2 L three-necked glass flask equipped with stirrer,condenser cooler and temperature measuring probe. The reaction mixturewas heated while stirring to 80° C. under nitrogen atmosphere. Then 10wt % was added of a pre-emulsified monomer mixture consisting of intotal 179 gram demineralized water, 8.6 gram SLS (30 wt % in water),336.1 gram BMA, 93.0 gram BA, 76.3 gram iBOA, and 7.9 gram AA. Thereaction mixture was further heated to 78° C. and then a mixture of 0.5gram APS and 4.2 gram demineralized water was added. The reactionmixture was then heated to 85° C. and kept at this temperature for 10minutes. An initiator feed mixture of 1.1 gram APS and 107 gramdemineralized water and the remaining 90 wt % of the pre-emulsifiedmonomer feed were then gradually added as parallel feeds to the reactionmixture over a time period of 2 hours. The reaction mixture was thenkept for 30 minutes at 85° C. A post reaction with tert-butylhydroperoxide and isoascorbic acid was performed to react any residualmonomer. The resultant emulsion was then cooled to room temperature. ThepH of the latex was adjusted to 8.0 by addition of ammonia.

Comparative Example 5 was prepared using a similar recipe and procedureas applied for Comparative Example 4, but now the monomer feed mixtureconsisted of in total 132 gram demineralized water, 8.6 gram SLS (30 wt% in water), 270.2 gram BMA, 74.8 gram BA, 152.6 gram iBOA, and 15.7gram AA.

The properties of the final prepared acrylic dispersions are given inTable 2. All latices, except those of Comparative Examples 1a and 1b,were processed with little or no fouling and/or sediment formation.Final free monomer levels were all well below 500 ppm.

TABLE 2 Viscosity Particle (Brook- size Mn Mw Exper- Solids¹⁾ pH field)(DLS) (GPC) (GPC) iment [%] [—] [mPa · s] [nm] [kg/mol] [kg/mol] Example1 31.8 8.0 60 66 15.5 154 Example 2 35.1 8.2 98 68 23.5 173 Example 333.0 7.8 50 67 17.9 200 Example 4 28.8 7.5 45 118 20.5 246 Comp 34.0 7.923 428 18.6 118 Ex 1c Comp 29.8 7.9 155 71 33.4 174 Ex 2 Comp 39.6 8.021 99 17.2 250 Ex 3 Comp 34.6 7.4 10 92 36.6 410 Ex 4 Comp 34.9 7.8 10471 30.1 226 Ex 5 ¹⁾gravimetrically determined

Examination of Dry and Wet Adhesion Level to ABS, PVC, Polystyrene (PS),Polycarbonate (PC) and Untreated Polypropylene (Untreated PP)

The level of dry and wet adhesion to various plastic substrates wasdetermined using a Gitterschnitt test (see test descriptions). Prior totesting all Examples and Comparative Examples were adjusted to a solidslevel of about 30% with demineralized water and formulated with 10 wt %butyl glycol and 1 wt % Byk 346, based on total acrylic dispersion. Theformulations were allowed to stand overnight prior to use.

Plastic test panels of ABS (Vikureen ABS white, Vink), PVC (PVC XT lightgrey, Vink), PS (Vikureen PS XT white, Vink), PC (Lexan 9030 Exell Dtransparent, GE Plastics) and PP (Simona PP XT naturel, Vink) of about12 cm×20 cm×0.2 cm were cleaned with ethanol and coated with theformulated acrylic dispersions at a 50 μm layer thickness using awirerod. The coated panels were left to dry for at least 1 hour atapproximately 20° C., and then dried in an oven at 50° C. for a periodof 16 hours to make sure that all water and residual solvent was removedfrom the film. After this drying period the coated plastic plates wereleft for at least one hour at 20° C. The obtained dry films were thenexamined for dry and wet adhesion (Gitterschnitt, Gt).

Results Adhesion to Untreated Polypropylene Plates

For all Examples and Comparative Examples the level of dry and wetadhesion to untreated polypropylene plates was determined. Results aregiven in Table 3.

TABLE 3 Dry adhesion to untreated PP plate Wet adhesion to (Gt; 0 =excellent untreated PP plate Experiment and 5 = poor) (Gt; 0 = excellentand 5 = poor) Example 1 2 2 Example 2 0-1 0-1 Example 3 2-3 2 Example 42 2 Comp Ex 1c 5 5 Comp Ex 2 5 5 Comp Ex 3 5 5 Comp Ex 4 5 5 Comp Ex 5 55

The results given in Table 3 show that the Examples have much betteradhesion to untreated polypropylene than the Comparative Examples.

Results Adhesion to Oriented Polypropylene Foil

For Example 1 and Comparative Example 3 the level of dry adhesion tooriented polypropylene substrate (OPP foil) was determined using a tapetest. Prior to testing the acrylic dispersions of Example 1 andComparative Example 3 were formulated with 10 wt % on total dispersionof butyl glycol (added as 80 wt % in water). Only in case of adhesiontesting to the very hydrophobic untreated polypropylene substrate anadditional amount of 0.25 wt % on total dispersion of Surfynol PSA-336(available from Air Products) was added together with the butyl glycol.The pH of the butyl glycol/water premix was adjusted to about 8 byammonia before addition. The formulations were tinted with Microlithblue to allow visual assessment of the adhesion test results.

Films of the tinted formulated dispersions were applied by a wire rod at6 microns wet onto the treated and untreated side of an orientedpolypropylene substrate foil (50MB-210 available from Exxon Mobil). Thecasted films were dried for 1 minute in an oven at 80° C. The obtaineddry films were left for at least 2 hours at 20° C. and then examined foradhesion properties by performing a tape test. Prior to application thesurface tension of the treated and untreated side of the orientedpolypropylene substrate surface was measured as defined in DIN ISO 8296in accordance with ASTM D 2578-04a by using test inks available fromSoftal Electronic (Germany).

The test results obtained for Example 1 and Comparative Example 3 aregiven in Table 4.

TABLE 4 Wetting Tape test Experiment (0-5; 5 = good) (% coating removed)Locus of failure treated oriented polypropylene foil (surface tension34-36 Dynes/cm) Example 1 4 0% no failure Comp Ex 3 3-4 100% adhesiveuntreated oriented polypropylene foil (surface tension <<34 Dynes/cm)Example 1 5 <10% cohesive Comp Ex 3 5 100% adhesive

The results given in Table 4 show that Example 1 provides very goodadhesion to both the treated and untreated side of the OPP foil, whereasComparative Example 3 gives no adhesion at all.

Dry and Wet Adhesion to ABS, Polystyrene (PS), Polyvinyl Chloride (PVC)and Polycarbonate (PC)

For Examples 1 to 5 and Comparative Example 1c the level of dry and wetadhesion to ABS, PS, PVC and PC was determined using the Gitterschnitttest, where 0=excellent adhesion and 5=very poor adhesion. Results aregiven in Table 5.

TABLE 5 ABS PS PVC PC Experiment dry/wet (Gt) dry/wet (Gt) dry/wet (Gt)dry/wet (Gt) Example 1 0/1 0-1/1   0-1/0-1 0-1/1   Example 2   0/0-1 0/00/0   0/0-1 Example 3 0/1 0/0 0/0   1/1-2 Example 4 1/1 0/1 0/1 0-1/1  Comp Ex 1c 0/2 0/1 0-1/5   1/4

The results given in Table 5 show that the Examples have better overallwet adhesion than Comparative Example 1c.

Test Descriptions Dry and Wet Adhesion to Plastic Substrate Plates

The level of dry adhesion to untreated plastic substrates (ABS, PVC,polystyrene, polycarbonate, and untreated polypropylene) was determinedusing a cross-cut test (“Gitterschnitt” (Gt) test in accordance withASTM D 3002/D 3359 and DIN EN ISO 2409). A cross-cut was made onto thedried coated plastic plates using a cross-cut knife (Byk-5120). A selfadhesive tape (Sellotape™ 25 mm from Henkel Consumer Adhesives) wasapplied under uniform pressure onto the coated substrate, covering thecross-cut, where after the tape was torn off in a single movement. Thistape test was then repeated with the tape placed over the cross-cut in aperpendicular direction to the first test. The degree of dry adhesion ofthe coating onto the plastic substrate was then classified with a scalefrom 0 to 5 (according ISO Class 0-5 (Gt)) by determining the amount ofcoating that is detached or flaked partly or wholly along the edges ofthe cuts, where 0 means that the cross-cut area is not affected(excellent adhesion); 1 means that the affected cross-cut area is notsignificantly greater than 5%; 2 means that the affected cross-cut areais significantly greater than 5%, but not significantly greater than15%; 3 means that the affected cross-cut area is significantly greaterthan 15%, but not significantly greater than 35%; 4 means that theaffected cross-cut area is significantly greater than 35%, but notsignificantly greater than 65%; 5 means any degree of flaking thatcannot even be classified by classification 4 (very poor adhesion).

To determine the level of wet adhesion a piece of cotton wool soakedwith demineralized water was placed on an area of the coated substrate.After 4 hours at 20 (±3° C.) the wet cotton wool was removed and thecoating was carefully dried with a tissue. The level of wet adhesion wasthen determined according the cross-cut test method used for determiningthe dry adhesion, where the cross-cut was made onto the coated area thatwas exposed to the water.

Adhesion to Oriented Polypropylene Foil

A self adhesive tape (Sellotape™ 25 mm from Henkel Consumer Adhesives)was applied under uniform pressure onto a dry coating layer applied ontoboth the treated and untreated side of the oriented polypropylenesubstrate, where after the tape is torn off with a non-continuousmovement. The adhesion properties of the coating onto the polypropylenesubstrate were investigated by assessing the amount of coating that isadhered to the tape after removing the tape from the coating. Optimaladhesion is obtained at “0% coating removed”. In addition the main locusof failure was visually determined as being cohesive, i.e. failurewithin the coating, or adhesive, i.e. between the coating-substrateinterface. Cohesive failure typically indicates a strong interactionbetween the coating and the substrate, whereas adhesive failure means aweak interaction between the coating and the substrate.

Wetting

The wetting behavior of the coating onto both the treated and untreatedside of the oriented polypropylene substrate surface was visuallyassessed and classified from a scale of 0 to 5, where 0 means very poorwetting and 5 means excellent wetting.

1. A process for preparing an aqueous coating composition comprising ablock copolymer and a polymer P; wherein the block copolymer comprisesat least blocks [A]_(x)[B]_(y), where at least block [A] is obtained bya controlled radical polymerisation of at least one ethylenicallyunsaturated monomer via a reversible addition-fragmentation chaintransfer (RAFT) mechanism; where block [A] comprises: i) 0 to 50 mol %of ethylenically unsaturated monomer units bearing crosslinkingfunctional groups; ii) 20 to 100 mol % of ethylenically unsaturatedmonomer units bearing water-dispersing functional groups; iii) 0 to 50mol % of ethylenically unsaturated monomers units selected from linearor branched C₁ to C₈ alkyl(meth)acrylate monomers; iv) 0 to 5 mol % ofethylenically unsaturated monomer units bearing plastic adhesionpromoting functional groups; and v) 0 to 10 mol % of ethylenicallyunsaturated monomers units different from those from i), ii), iii)+iv);where i), ii), iii), iv)+v) add up to 100%; block [A] has an averagedegree of polymerisation x, where x is an integer from 3 to 80; whereblock [B] comprises: i) 0 to 5 mol % of ethylenically unsaturatedmonomer units bearing crosslinking functional groups; ii) 0 to 15 mol %of ethylenically unsaturated monomer units bearing water-dispersingfunctional groups; iii) 0 to 50 mol % of ethylenically unsaturatedmonomers units selected from linear or branched C₁ to C₈alkyl(meth)acrylate monomers; iv) 20 to 100 mol % of ethylenicallyunsaturated monomer units bearing plastic adhesion promoting functionalgroups; and v) 0 to 10 mol % of ethylenically unsaturated monomers unitsdifferent from those from i), ii), iii)+iv); where i), ii), iii), iv)+v)add up to 100%; block [B] has an average degree of polymerisation y,where y is an integer >10, where y>x; and where polymer P is obtained inthe presence of the block copolymer by an emulsion polymerisationprocess, and comprises: i) 0 to 20 wt % of ethylenically unsaturatedmonomer units bearing crosslinking functional groups; ii) 0 to 15 wt %of ethylenically unsaturated monomer units bearing water-dispersingfunctional groups; iii) 50 to 100 wt % of ethylenically unsaturatedmonomers units selected from linear or branched C₁ to C₈alkyl(meth)acrylate monomers; iv) 0 to 50 wt % of ethylenicallyunsaturated monomer units bearing plastic adhesion promoting functionalgroups; and v) 0 to 10 mol % of ethylenically unsaturated monomers unitsdifferent from those from i), ii), iii)+iv); where i), ii), iii), iv)+v)add up to 100%.
 2. A process according to claim 1, where block [A] isobtained and/or obtainable by a controlled radical polymerisation of atleast one ethylenically unsaturated monomer via a reversibleaddition-fragmentation chain transfer mechanism in solution in thepresence of a control agent and a source of free radicals.
 3. A processaccording to claim 2, in which the aqueous coating composition iscapable of being applied to plastic substrates to form a coatingthereon.
 4. A process according to claim 1, where block [B] is obtainedand/or obtainable by a controlled radical polymerisation of at least oneethylenically unsaturated monomer via a reversibleaddition-fragmentation chain transfer mechanism in solution in thepresence of a control agent and a source of free radicals.
 5. A processaccording to claim 1, wherein the ethylenically unsaturated monomerunits bearing plastic adhesion promoting functional groups are selectedfrom the group consisting of C₆ to C₂₀ (preferably C₆ to C₁₅) optionallysubstituted alkyl, cyclo alkyl and or aryl(meth)acrylate monomers,styrenic monomers, C₆ to C₂₀ (preferably C₆ to C₁₅) optionallysubstituted alkyl(meth)acrylamide monomers, vinylic monomers andmixtures thereof.
 6. A process according to claim 1, where, when thesubstrate is polyolefinic, then component iv) of Block [B] comprises atleast 50 mol % of isobornyl(meth)acrylate.
 7. A process according toclaim 1, wherein the control agent is selected from the group consistingof dithioesters, thioethers-thiones, trithiocarbonates,dithiocarbamates, xanthates and mixtures thereof.
 8. A process accordingto claim 1 where polymer P is at least partially grafted to blocks[A][B].
 9. An aqueous coating composition obtained and/or obtainable bya process as claimed in claim
 1. 10. An aqueous coating composition asclaimed in claim 9, which is capable of being applied to plasticsubstrates to form a coating thereon.
 11. A mixture of i) blockcopolymer comprising at least blocks [A]_(x)[B]_(y), and ii) polymer P;where said mixture is obtained and/or obtainable by a process as claimedin claim
 1. 12. A block copolymer-polymer comprising as componentsthereof i) block copolymer comprising at least blocks [A]_(x)[B]_(y) andii) polymer P, where said blockcopolymer-polymer is obtained and/orobtainable by a process as claimed in claim
 1. 13. A coating obtainedand/or obtainable from a coating composition as claimed in claim 9and/or block copolymer-polymer.
 14. A substrate and/or article coatedwith a coating as claimed in claim
 13. 15. A coated substrate and/orcoated article as claimed in claim 14, where the substrate and/orarticle comprises hydrophobic plastic.
 16. A method of coating asubstrate and/or article comprising the steps of i) applying a coatingcomposition as claimed in claim 9 and/or block copolymer-polymer to thesubstrate and/or article; and ii) drying the substrate and/or article toform a coating thereon.
 17. A method as claimed in claim 16, where thesubstrate and/or article comprises hydrophobic plastic.
 18. A coatedsubstrate and/or coated article obtained and/or obtainable by a methodas claimed in claim
 16. 19. Use of a coating composition as claimed inclaim 9 and/or block copolymer-polymer to coat a substrate and/orarticle.
 20. Use of a coating composition as claimed in claim 9 and/or asubstrate and/or article to provide coatings on at least one materialselected from the group consisting of: plastic substrates foams;surfaces having low surface energy; hydrophobic substrates; polyolefins;any combinations thereof; and any mixtures thereof.
 21. A use as claimedin claim 20, where the coating is applied to at least one articleselected from the group consisting of: vehicles; consumer electronicarticles; furniture; household articles, biomedical articles, anycombinations thereof and any mixtures thereof.
 22. A method ofmanufacture of a coating composition as claimed in claim 9 and/or asubstrate and/or article for the purpose of being used in at least oneof the applications.